Heating device

ABSTRACT

A heating apparatus  11 A includes a susceptor having a heating face  12   a  of heating a semiconductor. The susceptor includes a plate shaped main body  13  and a surface corrosion resistant layer  14  including the heating face. The surface corrosion resistant layer  14  is made of a ceramic material comprising magnesium, aluminum, oxygen and nitrogen as main components. The ceramic material comprises a main phase comprising magnesium-aluminum oxynitride phase exhibiting an XRD peak at least in 2θ=47 to 50° by CuKα X-ray.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present indention relates to an apparatus of heating semiconductors.

2. Description of Related Art

In a system of producing semiconductors used far dry process or plasmacoating in semiconductor production, it has been used halogen-basedplasma such as F, Cl or the like Easing high reactivity for etching orcleaning. It is thus required, for a member equipped to sucksemiconductor production system, high corrosion resistance, so that ithas been generally used a member of an anti-corrosive metal such asaluminum with alumite treatment, HASTELLOY or the like or a ceramicmaterial. Especially, it is necessary high corrosion resistance and lowparticle generation properties for an electrostatic chuck or heatermember supporting and fixing a Si wafer, so that it has bees used a highcorrosion resistant ceramic member such as aluminum nitride, alumina,sapphire or the like. As these materials are used for a long time, theyare gradually corroded to induce particle generation, so that it hasbeen demanded a material whose corrosion resistance is further improved.For attending such demands, it is studied to use, as the material,magnesia, spinel (MgAl₂O₄) or a composite material thereof whosecorrosion resistance is higher than that of alumina (For example, Patentdocument 1: U.S. Pat. No. 3,559,426B).

It is further known a ceramic heater used for heating wafers. In suchceramic heaters, temperature uniformity of the heater is required forheating the wafer uniformly. For example, according to the disclosure ofPatent Document 2 (Patent Publication No. H08-073280A), a heatresistance is embedded in an aluminum nitride based ceramic plate, towhich an aluminum nitride based shaft is bonded to provide a ceramicheater. According to the descriptions of Patent document 3 (PatentPublication No. 2003-288975A), in a ceramic heater with a shaft, acontent of metal carbide in a heat resistance is lowered to reduce thedeviation of the carbide content in the heat resistance depending on thepositions, so that the temperature distribution on its heating face isreduced.

SUMMARY OF THE INVENTION

Usually, in semiconductor production process, a corrosive gas such ashalogen based gas or the like is used for cleaning of a system forpreventing contamination of a wafer. Further, it is required temperatureuniformity on the wafer for forming a film uniformly on the wafer. As amember of holding and further heating an Si wafer in a semiconductorproduction system, it has been widely used a ceramic heater made of AlN(aluminum nitride) as exiting art, resulting in good temperatureuniformity on the wafer in initial stage. However, AlN is corroded feycleaning with the corrosive gas, so that the shape and roughness of thesurface of the heater are changed and the temperature distribution isthereby changed during its use life. It is problematic that thetemperature uniformity cannot be maintained.

An object of the present invention is, in a ceramic heating apparatusused for processing semiconductors, to reduce particles when theapparatus is used under halogen corrosive gas or its plasma atmosphere,and to maintain good temperature uniformity for a long period of time.

The present invention provides a heating apparatus comprising asusceptor comprising a heating face of heating a semiconductor. Thesusceptor comprises a plate shaped main body and a surface corrosionresistant layer for facing said heating face, and the surface corrosionresistant layer comprises a ceramic material comprising main componentscomprising magnesium, aluminum, oxygen and nitrogen, and the ceramicmaterial comprises a main phase comprising magnesium-aluminum oxynitridephase exhibiting an XRD peak at least in 2θ=47 to 50° taken by usingCuKα ray.

The ceramic material of the present invention includes theMagnesium-aluminum oxynitride phase as its main phase, and is superiorin corrosion resistance against strong corrosive gas such as halogenbased gas, compared with aluminum nitride. By forming the surfacecorrosion resistant layer of the susceptor with such ceramic material,the surface state is not susceptible to change by the corrosion when itis used for a long time under corrosive condition. As a result, itbecomes possible to maintain good temperature uniformity on a wafer fora long time.

Further, it is possible to form the plate shaped main body with adifferent material having a thermal conductivity higher than that of theceramic material. It is thereby possible to facilitate thermalconduction in planar direction on the susceptor so that the temperatureuniformity on the wafer can be further improved.

BRIEF DESCRIPTION OF THE DRAWINGS

The patent or application file contains at least one drawing executed incolor. Copies of this patent or patent application publication withcolor drawing(s) will be provided by the Office upon request and paymentof the necessary fee.

FIG. 1 is an XRD analytical chart obtained in Experiment 1.

FIG. 2 is EPMA element mapping images obtained in Examples 1 and 4.

FIG. 3 is an XRD analytical chart obtained in Experiment 7.

FIG. 4 is an XRD analytical chart obtained in Experiment 10.

FIG. 5 is a cross sectional view schematically showing a heatingapparatus according to a reference embodiment.

FIG. 6 is a front view schematically showing appearance of a heatingapparatus according to a reference embodiment.

FIG. 7 is a cross sectional view schematically showing a heatingapparatus 11A according to an embodiment of the present invention.

FIG. 8 is a front view schematically showing appearance of a heatingapparatus 11A according to an embodiment of the present invention.

FIG. 9 is a cross sectional view schematically showing a heatingapparatus 11B according to an embodiment of the present invention.

FIG. 10 is a cross sectional view schematically showing a heatingapparatus 11B according to an embodiment of the present invention.

FIG. 11 is a cross sectional view schematically showing a heatingapparatus 11D according to an embodiment of the present invention.

FIG. 12 is a flow chart showing a process of producing a heatingapparatus according to an embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

The novel ceramic material used in the present invention will bedescribed first, and details of the heating apparatus will be describedlater.

(Ceramic Material)

The inventors intensively studied corrosion resistance of a ceramicmaterial produced by molding a mixture of magnesium oxide, alumina andaluminum nitride powders and by sintering the mold by hot presssintering. As a result, it was found that considerably high corrosionresistance can be obtained by the ceramic material including a mainphase composed of magnesium-aluminum oxynitride having an XRD peak at aspecific position.

That is, the inventive ceramic material comprises main componentscomprising magnesium, aluminum, oxygen and nitrogen, and the ceramicmaterial comprises a main phase comprising magnesium-aluminum oxynitridephase exhibiting an XRD peak at least in 2θ=47 to 50° taken by usingCuKα ray.

The ceramic material of the present invention has corrosion resistancecomparable with, or superior than, that of spinel. Therefore, theinventive susceptor can endure against halogen based plasma such as F,Cl or the like used in a semiconductor production process for a longtime, so that it is possible to reduce an amount of particles generatedfrom the susceptor member. Moreover, even when the susceptor is used fora long time under corrosive condition, the change of the surface statedue to corrosion can be reduced, so that it is possible to obtain goodtemperature uniformity on a wafer for a long time.

The inventive ceramic material includes main components includingmagnesium, aluminum, oxygen and nitrogen, and the ceramic materialincludes a main phase comprising the magnesium-aluminum oxynitride phaseexhibiting an XRD peak at least in 2θ=47 to 50° taken by using CuKα ray.As the magnesium-aluminum oxynitride has corrosion resistance againsthalogen based plasma comparable with, or superior than, that of spinel,it is considered that the inventive ceramic material including theoxynitride as its main phase also exhibits high corrosion resistance.Further, the magnesium-aluminum oxynitride has corrosion resistancecomparable with that of spinel, and at the same time, can have a linearthermal expansion coefficient lower than that of spinel.

The inventive ceramic material may contain, as a sub phase, crystalphase of MgO—AlN solid solution composed of magnesium oxide to whichaluminum nitride is dissolved. The MgO—AlN solid solution is alsoanti-corrosive, so that it is not problematic if it is contained as asub phase. The XRD peaks at (200) and (220) faces of the MgO—AlN solidsolution taken by using CuKα ray may be observed in ranges of 2θ=42.9 to44.8° and 62.3 to 65.2° respectively which are between peaks of cubicphase of magnesium oxide and cubic phase of aluminum nitride,respectively. Further, XRD peak at (111) face may be observed in a rangeof 2θ=36.9 to 39°, which is between peaks of cubic phase of magnesiumoxide and cubic phase of aluminum nitride. Since it may be difficult todistinguish the peak at (111) face from the peaks corresponding with theother crystalline phases, only the XRD peaks at (200) face and (220)face may be observed in the above ranges. Similarly, it may be difficultto distinguish the peak at (200) face or the peak at (220) face from thepeaks corresponding with the other crystalline phases.

In the inventive ceramic material, for obtaining corrosion resistancecomparable with, or higher than, that of spinel, the content of AlNcrystal phase may preferably be lower and more preferably AlN crystalphase is not contained, because the corrosion resistance tends to bedeteriorated in the case that AlN crystal phase is contained as the subphase. Further, since the corrosion resistance of spinel is higher thanthose of alumina and AlN crystals, a small amount of spinel may becontained. However, since the corrosion resistance of spinel is inferiorto that of the inventive magnesium-aluminum oxynitride phase or MgO—AlNsolid solution, it is preferred that the content of spinel is lower. Onthe other hand, for lowering the linear thermal expansion coefficientwhile maintaining the corrosion resistance comparable with that ofspinel, a small amount of spinel or AlN crystal phase may be contained.

In the inventive ceramic material, for obtaining corrosion resistancecomparable with, or higher than, that of spinel, a molar ratio ofmagnesium/aluminum in powdery raw material may preferably be 0.20 orhigher and 2 or lower, and more preferably be 0.75 or higher and 2 orlower. In the case that the molar ratio of magnesium/aluminum is lowerthan 0.20, it might be concerned that an amount of generation of eitherof aluminum nitride, spinel and aluminum nitride would become large toresult in reduction of the superior anti-corrosion characteristics. Inthe case that the molar ratio of magnesium/aluminum exceeds 2, theMgO—AlN solid solution tends to become a main phase. On the other hand,for lowering the linear thermal expansion coefficient while maintainingthe corrosion resistance comparable with that of spinel, the molar ratioof magnesium/aluminum in the powdery raw material may preferably be 0.05or higher and 1.5 or lower, and more preferably be 0.1 or higher and 1or lower.

An open porosity of the inventive ceramic material may preferably be 5%or lower. Here, the open porosity means a value measured by Archimedeanmethod using pure water as an medium. In the case that the open porosityexceeds 5%, there would be a risk that the strength is lowered or thematerial itself would become susceptible to removal of grains and theresultant particle generation, and particle components tends to bestored in the pores during the processing of the material, which is notpreferred. Further, it is preferred that the open porosity is nearer tozero as possible. The lower limit of it is not particularly defined.

According to the inventive ceramic material, the linear thermalexpansion coefficient of the magnesium-aluminum oxynitride forming themain phase in a range of 40 to 1000° C. is 6 to 7 ppm/K. Thus, bychanging the ratios of the sub-components such as the MgO—AlN solidsolution (12 to 14 ppm/K), spinel (8 to 9 ppm/K), and aluminum nitride(5 to 6 ppm/K), the linear thermal expansion coefficient can becontrolled in a range of 5.5 to 10 ppm/K while maintaining the highcorrosion resistance. However, since spinel or aluminum nitride is lowerin the corrosion resistance than the magnesium-aluminum oxynitride orMgO—AlN solid solution, the contents thereof may be preferably smaller.By adjusting the thermal expansion as such, it is possible to match thethermal expansion with those of aluminum oxide, yttrium oxide andaluminum nitride used for members for semiconductor production systems.Alternatively, the difference of the thermal expansion coefficients canbe reduced. By these, it is possible to laminate or adhere the inventiveceramic material onto a prior material. It is thereby possible to usethe inventive ceramic material with high corrosion resistance for asurface part (first structural body) and to use the prior material as abase material for a lower part (second structural body). Such layeredstructure and the adjustment of thermal expansion are particularlyeffective especially in the co-sintering process. Among them, by using amaterial mainly composed of aluminum nitride as the base material of thesecond structural body, it becomes easier to maintain a high thermalconductivity and to maintain the surface temperature uniformity of theceramic material with high corrosion resistance. Such construction isespecially effective in a system of producing semiconductors ofso-called heater embedded type.

The inventive ceramic material may be used for a laminated body having afirst structural body utilizing the ceramic material and a secondstructural body including, as its main phase, at least one of aluminumnitride, yttrium oxide and aluminum oxide. Further, it may have astructure in which the first and second structural bodies are laminatedor bonded with each other. By applying the first structural body withhigh corrosion resistance and the second structural body with the otherproperty (for example heat transmission or mechanical strength), it isthereby possible to further improve the corrosion resistance as well asthe other properties. Here, the first structural body may be a thinfilm, plate body or laminated body formed with the ceramic materials.Further, the second structural body may be composed of a thin film,plate-shaped body or laminated body having aluminum nitride, yttriumoxide and aluminum oxide as its main phase. Besides, the bonding may bemade according to any embodiment, and for example may be bonded bysintering or an adhesive agent, for example.

At this time, the first and second structural bodies may be bonded witheach other through an intermediate layer. By the intermediate layer, itis thereby possible to further prevent the peeling of the first andsecond structural bodies due to, for example difference of thermalexpansion coefficients. The intermediate layer may be a layer havingproperties between those of the first and second structural bodies. Theintermediate layer may be, for example, a layer of mixing the mainphases of the first and second structural bodies. Further, theintermediate layer may include a plurality of layers having differentcomponents or ratios of components. It is thereby possible to provideproperties of a functionally graded material.

Further, a difference of linear thermal expansion coefficients of thefirst and second structural bodies may be 0.3 ppm or smaller, and thefirst and second structural bodies may be directly bonded with eachother. Since the difference of the linear thermal expansion coefficientsof the first and second structural bodies is made thus small, it ispossible to avoid the risk of cracks or peeling, in the case that bothstructural bodies are bonded with each other at a high temperature (forexample bonded by sintering) or the laminated body is repeatedly used athigh and low temperatures.

(Production of Ceramic Material)

The inventive ceramic material can be produced by molding powderymixture of magnesium oxide, alumina and aluminum nitride and then bysintering. For example, for obtaining high corrosion resistancecomparable with, or higher than, that of spinel, 15 mass percent or moreand 66.2 mass percent or less of magnesium oxide, 63 mass percent orless of alumina and 57.7 mass percent or less of aluminum nitride may bemixed to obtain powdery mixture, which may be molded and then sintered.Further, 37 mass percent or more and 66.2 mass percent or less ofmagnesium oxide, 63 mass percent or less of alumina and 57.7 masspercent or less of aluminum nitride may be mixed to obtain powderymixture, which may be molded and then sintered. On the other hand, forlowering the linear thermal expansion coefficient to improve temperatureuniformity while maintaining the corrosion resistance comparable withthat of spinel, 5 mass percent or more and 60 mass percent or less ofmagnesium oxide, 60 mass percent or less of alumina and 90 mass percentor less of aluminum nitride may be mixed to obtain powdery mixture,which may be molded and then sintered. Further, the sinteringtemperature may preferably be 1750° C. or higher. In the case that thesintering temperature is lower than 1750° C., it would be a risk thatthe targeted magnesium-aluminum oxynitride would not be generated, whichis not preferred. Besides, although the upper limit of the sinteringtemperature is not particularly limited, it may be 1850° C. or 1900° C.,for example. Further, hot press sintering may be preferably applied forthe sintering, and a pressure during the hot press sintering maypreferably be set in a range of 50 to 300 kgf/cm². Atmosphere during thesintering may preferably be that which does not affect the sintering ofthe oxide raw material, and may preferably be an inert atmosphere suchas nitrogen, argon, helium atmosphere or the like. The pressure for themolding is not particularly limited and may be adjusted at any pressureas far as it is possible to maintain the shape.

(Heating Apparatus)

According to a preferred embodiment, the heating apparatus of thepresent invention includes a susceptor having a heating face for heatinga semiconductor and a supporting part joined to a back face of thesusceptor. FIGS. 5 to 8 schematically illustrate such heating apparatus.FIGS. 5 and 6 shows a heating apparatus 1 of a reference example andFIGS. 7 and 8 shows a heating apparatus 11A of the inventive example.

Susceptors 2 and 12A are plate-shaped, and upper faces 2 a and 12 a ofthe susceptors 2 and 12A are semiconductor heating faces. Thesemiconductor heating faces 2 a and 12 a are not necessarily flat, andthe heating face may be roughened, or it may be formed a groove having asize comparable with that of a substrate or a groove for flowing purgegas. A supporting part 3 is bonded to a lower face (back face) 2 b or 12b of the susceptor. According to the present example, the supportingpart is tube shaped and a member 5 for supplying electricity iscontained inside of the supporting part 3. The member for supplyingelectricity is connected to a heat resistor 4 embedded within thesusceptor.

The susceptor is plate shaped and preferably, substantially circulardisk shaped. Although the size of the susceptor is not particularlylimited, the diameter is 280 to 380 mm and thickness is 8 to 20 mm, forexample. Further, although an outer diameter of a bonding part of thesusceptor and supporting part is not particularly limited, the diameteris 60 to 120 mm, for example. It is preferred that the supporting partincludes a step therein, a large size part 3 a is provided on the sideof the susceptor and a small size part 3 c is provided on the oppositeside with respect to the step. Flanges 3 b and 3 d are formed on endparts of the large size part 3 a and small size part 3 c, respectivelythe flange 3 b is not shown in the example of FIG. 5). Then, the endpart of the large size part is bonded to the back face of the susceptorso that the center axis of the supporting part is concentric with thatof the susceptor.

Here, although the heating member may preferably be embedded within thesusceptor, the heating member may be fitted to the susceptor.Alternatively, the heating member may be an outer heating member, suchas an infrared ray heating device, fitted at a position distant from thesusceptor.

Here, according to the comparative example shown in FIGS. 5 and 6, thewhole of the susceptor 2 is made of a homogeneous material. Contrary tothis, according to the example shown in FIGS. 7 and 8, the susceptor 12Aincludes a plate shaped main body 13 and a surface corrosion resistantlayer 14 covering a surface 13 a of the plate shaped main body 13.According to the present example, a side face 13 c and a hack face 13 bof the plate shaped main body 13 are not covered by a corrosionresistant layer. According to the present invention, the surfacecorrosion resistant layer is made of the ceramic material. The heatgenerator 4 is embedded in the plate shaped main body 13.

Further, according to a heating apparatus 11B shown in FIG. 9, asusceptor 12B includes the plate shaped main body 13 and the surfacecorrosion resistant layer 14 covering the surface 13 a of the plateshaped main body 18. According to the present example, the side face 13c and back face 13 b of the plate shaped main body 13 are not coveredwith a corrosion resistant layer. According to the present invention,the surface corrosion resistant layer 14 is formed of the ceramicmaterial. In addition to this, an intermediate layer 17 is providedbetween the surface corrosion resistant layer 14 and the surface 13 a ofthe plate shaped main body 13. It is thus preferred for maintaining thepeeling strength of the surface corrosion resistant layer to the plateshaped main body, even when heating and cooling are repeated.

Further, according to a heating apparatus 11C shown in FIG. 10, asusceptor 12C includes the plate shaped main body 13, the surfacecorrosion resistant layer 14 covering the surface 13 a of the plateshaped main body 13, and a side face corrosion resistant layer 15covering the side face 13 a of the plate shaped main body 13. Accordingto the present example, the back face 13 b of the plate shaped main body13 is not covered with a corrosion resistant layer. According to thepresent invention, the surface corrosion resistant layer 14 and sideface corrosion resistant layer 15 are formed of the ceramic material. Ifthe side face of the susceptor is corroded, it may not only become acause of particles, but also change the thermal radiationcharacteristics from the side face so that the temperature uniformity onwafer is adversely influenced. According to the present embodiment, itis possible to prevent the corrosion on the wafer as well as on the sideface. Besides, the intermediate layer 17 as described above may beprovided between the surface corrosion resistant layer 14 and thesurface 13 a of the plate shaped main body 13. Further, the intermediatelayer 17 as described above may be provided between the side facecorrosion resistant layer 15 and the side face 13 c of the plate shapedmain body 13.

Further, according to a heating apparatus 11D shown in FIG. 11, asusceptor 12D includes the plate shaped main body 13, the surfacecorrosion resistant layer 14 covering the surface 13 a of the plateshaped main body 13, and a back face covering layer 16 covering the backface 13 b of the plate shaped main body 13. According to the presentexample, the side face 13 c of the plate shaped main body 13 is notcovered with a corrosion resistant layer. According to the presentinvention, the surface corrosion resistant layer 14 and back facecovering layer 16 are formed of the ceramic material. Besides, theintermediate layer 17 as described above may be provided between thesurface corrosion resistant layer 14 and the surface 13 a of the plateshaped main body 13. Further, the intermediate layer 17 as describedabove may be provided between the back face covering layer 16 and theback face 13 b of the plate shaped main body 13.

In the case that a material having a thermal conductivity higher thanthat of the ceramic material is used as a material of the plate shapedmain body, the temperature uniformity on wafer is improved due to thethermal conduction in the plate shaped main body as a whole. However, inthis case, since an amount of heat radiation from the back face 13 b ofthe plate shaped main body 13 is also increased, there is a possibilitythat the temperature uniformity on wafer may be deteriorated due touneven thermal radiation. According to the present embodiment, since theback face covering layer made of the ceramic material is provided on theside of the back face of the plate shaped main body, it is possible notonly to realize the corrosion resistance on the side of the back face,but also to reduce the thermal radiation from the back face of thesusceptor as a whole so that the temperature uniformity on wafer can befurther improved.

According to the present invention, although the susceptor is formed ofthe ceramic material, a material forming the supporting part 3 (socalled shaft) is not particularly limited and includes the followings.

The ceramic material of the present application, aluminum nitride,alumina, magnesium oxide, spinel

Preferably, the material of the supporting part 3 is made the ceramicmaterial described above. Even in this case, however, the ceramicmaterials forming the susceptor and supporting part is not necessarilyidentical and may be of compositions different from each other in thecomposition range as described above.

A wire conductor may be bent and processed to a wounded body, which maybe used as the heating member, for example. The wire diameter of theheating member is about 0.3 to 0.5 mm, and the winding diameter in thecase of a coil shaped member is about 2 to 4 mm and the pitch is about 1to 7 mm. The “winding diameter” referred to herein means an innerdiameter of the coil forming the heating member.

As the shape of the heating member, in addition to the coil shape,various shapes may be applied such as ribbon, mesh, coil spring, sheet,printed electrode or the like. Further, in a part adjoining a throughhole formed for supplying purge gas, lift pin or the like, the patternof the heating member 12 may be optionally changed, for example, theheating member 12 may be turned away from the through hole. As thematerial of the heating member 12, it may be preferably used aconductive material with a high melting point such as molybdenum (Mo),tungsten (W), niobium (Nb) or the like.

In the susceptor of the heating apparatus, it may be embedded a radiofrequency electrode for generating plasma over the susceptor. A materialforming the radio frequency electrode may be those described above forthe heating member.

(Materials of Plate Shaped Main Body and Intermediate Layer)

According to the inventive ceramic material, the linear thermalexpansion coefficient of the magnesium-aluminum oxynitride forming themain phase in a range of 40 to 1000° C. 6 to 7 ppm/K. Thus, by changingthe ratios of the sub-components such as the MgO—AlN solid solution (12to 14 ppm/K), spinel (8 to 9 ppm/K), and aluminum nitride (5 to 6ppm/K), the linear thermal expansion coefficient can be controlled in arange of 5.5 to 10 ppm/K while maintaining the high corrosionresistance. However, since spinel or aluminum nitride is lower in thecorrosion resistance than the magnesium-aluminum oxynitride or MgO—AlNsolid solution, the contents thereof may be preferably smaller. Byadjusting the thermal expansion as such, it is possible to match thethermal expansion with those of aluminum oxide, yttrium oxide andaluminum nitride used for members for semiconductor production systems.It is thereby possible to laminate or adhere the inventive ceramicmaterial onto a prior material.

Specifically, the materials of the plate shaped main body includealuminum oxide, yttrium oxide, aluminum nitride, magnesium oxide,silicon nitride and spinel, and may particularly preferably be aluminumoxide, yttrium oxide or aluminum nitride.

In particular, by forming the plate shaped main body with a materialincluding aluminum nitride as its main phase, it is possible to maintainhigh thermal conductivity and easier to maintain the surface temperatureof the corrosion resistant ceramic material uniform.

It is not particularly limited a method of bonding the plate shaped mainbody and each of the corrosion resistant layers and back face coveringlayer. Both may be bonded with each other by, for example integratedsintering or an adhesive.

Such adhesive includes a silicon based adhesive, acrylic resin basedadhesive and Al alloy adhesive.

According to a preferred embodiment, a difference between the thermalexpansion coefficient of the plate shaped main body and that of thecorrosion resistant layer or the back face covering layer is 0.3 ppm/Kor smaller. In this case, when the plate shaped main body and thecorrosion resistant layer or back face covering layer are bonded witheach other at a high temperature (for example bonded by integratedsintering) or when the laminated body is repeatedly used at high and lowtemperatures, the risk of cracks and peeling can be avoided.

As described above, the plate shaped main body and each of the corrosionresistant layer and back face covering layer may be bonded through theintermediate layer. It is thereby possible to further prevent thepeeling of the corrosion resistant layer and back face covering layerdue to the difference of the thermal expansion, for example. Theintermediate layer is made a layer whose properties are between those ofthe plate shaped main body and the corrosion resistant layer or backface covering layer.

Specifically, the intermediate layer may be a composite ceramicsobtained by sintering mixture of the ceramic material described aboveand materials for the plate shaped main body.

Further, the intermediate layer may be composed of a plurality of layersand the compositions of the intermediate layers may be made differentform each other to form a graded material layer.

(Halogen Based Corrosive Gas)

The inventive susceptor is superior in the corrosion resistance againstthe halogen based corrosive gas and its plasma, and especially excellentin the corrosion resistance against the following halogen basedcorrosive gasses, the mixtures and plasmas.

NF₃, CF₄, ClF₃, Cl₂, BCl₃, HBr

EXAMPLES

(Production and Evaluation of Ceramic Material)

Preferred applications of the present invention will be described)below. As MgO, Al₂O₃ and AlN raw materials, they were used commercialproducts each having a purity of 99.9 mass percent or higher and anaverage particle size of 1 μm or lower. Here, as about 1 percent ofoxygen is inevitable in the AlN raw material, the above described purityis calculated after oxygen content is excluded from the impuritycontents. Further, even in the case that it is used MgO material havinga purity of 99 mass percent or higher, it could be produced a ceramicmaterial comparable with that produced by using MgO material having apurity of 99.9 mass percent or higher.

1. Ceramic Material

First, it will be described the ceramic material containing magnesium,aluminum, oxygen and nitrogen as the main components (Experiments 1 to19). Besides, the experiments 1 to 3 and 6 to 16 correspond to inventiveexamples and experiments 4, 5 and 17 to 19 correspond to comparativeexamples.

Experiments 1 to 3

(Formulation)

Raw materials of MgO, Al₂O₃ and AlN were weighed according to the mass %shown in table 1, and then wet-mixed using isopropyl alcohol as asolvent, nylon pot and alumina grinding stone with a diameter of 5 mmfor 4 hours. After the mixing, slurry was collected and dried innitrogen flow at 110° C. Thereafter, the dried matter was passed througha sieve of 30 mesh to obtain formulated powder. Besides, the molar ratioof Mg/Al in the formulated powder was 1.2

(Molding)

The formulated powder was subjected to uniaxial press molding at apressure of 200 kgf/cm² to produce a disk-shaped molded body haying adiameter of about 35 mm and a thickness of about 10 mm, which was thencontained in a graphite mold for sintering.

(Sintering)

The disk-shaped body was subjected to hot press sintering to obtain theceramic material. The hot press sintering was performed at a pressure of200 kgf/cm² and at a sintering temperature (the maximum temperature)shown in table 1, in Ar atmosphere until the completion of thesintering. The holding time at the sintering temperature was made 4hours.

Experiment 4

The ceramic material was obtained according to the same procedure as theExperiment 1, except that raw materials of MgO and Al₂O₃ were weighedaccording to the mass % shown in table 1.

Experiment 5

The ceramic material was obtained according to the same procedure as theExperiment 1, except that the sintering temperature was set at 1650° C.

Experiments 6 to 12

The ceramic material was obtained according to the same procedure as theExperiment 1, except that raw materials of MgO, Al₂O₃ and AlN wereweighed according to the mass % shown in table 1 and that the sinteringtemperature was made that shown in table 1.

Experiments 13 to 19

The ceramic material was obtained according to the same procedure as theExperiment 1, except that raw materials of MgO, Al₂O₃ and AlN wereweighed according to the mass % shown in table 1, that the sinteringtemperature was made that shown in table 1, and that the atmosphereduring the sintering was made N₂.

(Evaluation)

Each of the materials obtained in the experiments 1 to 19 was processedadapted for various evaluation procedures and the following evaluationswere performed. The result of each evaluation was shown in table 1.Besides, according to each of the experiments 1 to 19, another samplehaving a diameter of 50 mm was also produced and it was proved that thesamples provided evaluation results similar to those shown in table 1.

-   (1) Bulk Density, Open Porosity

They were measured according to Archimedean method using pure water asan medium.

-   (2) Evaluation of Crystal Phase

The material was ground using a mortar and its crystal phase wasidentified by an X-ray diffraction system. The condition of themeasurement was made CuKα, 40 kV, 40 mA, and 2θ=5 to 70° C. with asealed tube type X-ray diffraction system (“D8-ADVANCE” supplied byBruker AXS corporation) used.

-   (3) Etching Rate

The surface of each of the materials was polished to a mirror face,which was then subjected to corrosion resistance test using an ICPplasma corrosion resistance test system according to the followingconditions. The step of a masked face and exposed face was measured by astep gauge and the step value was divided by a test time period tocalculate the etching rate of each material.

ICP: 800 W, Bias: 450 W, Introduced gas: NF3/O2/Ar=75/35/100 sccm, 0.05Torr (6.67 Pa), Exposed time period: 10 hr, Temperature of sample: Roomtemperature

-   (4) Constituent Atoms

The detection, identification and analysis of content of eachconstituent atom were performed using EPMA.

-   (5) Average Linear Thermal Expansion Coefficient (40 to 1000° C.)

The measurement was performed using a dilatometer (supplied by BrukerAXS corporation) under argon atmosphere.

-   (6) Bending Strength

It was measured by bending strength test according to JIS-R1601.

-   (7) Measurement of Volume Resistivity

It was measured a method according to JIS-C2141 in air at roomtemperature (25° C.). The shape of a test sample was of a diameter of 50mm×(0.5 to 1 mm), and a main electrode with a diameter of 20 mm, a guardelectrode with an inner diameter of 30 mm and an outer diameter of 40 mmand an applying electrode with a diameter of 40 mm were formed, whilethe electrodes were made of silver. A voltage of 2 kV was applied and itwas read a current value at a time point 1 minute after the applicationof the voltage, and the current value was used to calculate a volumeresistivity at room temperature. Further, as to the Experiments 7 and 19(MgO sintered body), it was measured in vacuum (0.01 Pa or below) and at600° C. The shape of a test sample was of a diameter of 50 mm×(0.5 to 1mm), and a main electrode with a diameter of 2 mm, a guard electrodewith an inner diameter of 30 mm and an outer diameter of 40 mm and anapplying electrode with a diameter of 40 mm were formed while theelectrodes were made of silver. A voltage of 500 V/mm was applied and itwas read a current value at a time point 1 hour after the application ofthe voltage, and the current value was used to calculate a volumeresistivity. Further, in values of the volume resistivity shown in table1, “aEb” represents a×10^(b), and, for example, “1E16” represents1×10¹⁶.

(Evaluation Results)

FIG. 1 shows an XRD analytical chart obtained in Experiment 1. Further,XRD analytical charts obtained in Experiments 2 and 3 were proved to besubstantially same as that in the Experiment 1, the charts were notshown. Further, table 1 shows crystal phases detected in all of theExperiments 1 to 19. As shown in FIG. 1, the XRD analytical charts ofthe ceramic materials according to the Experiments 1 to 3 include aplurality of unidentified peaks (□ in FIG. 1) and peaks (◯ in FIG. 1)corresponding with the MgO—AlN solid solution composed of magnesiumoxide into which aluminum nitride is dissolved. The unidentified peaks“□” include peaks in a range of 2θ=47 to 49° (47 to 50°) which do notcorrespond with those of magnesia, spinel and aluminum nitride, and itwas assumed to be magnesium-aluminum oxynitride. Besides, these peaks ofthe magnesium-aluminum oxynitride are not identical with those of MgAlON(or MAGALON) shown in reference 1 (J. Am. Ceram. Soc., 93 [2] pages 322to 325 (2010)) and reference 2 (Japanese Patent Publication No.2008-115065A). Generally, the MgAlON is known to be spinel with Ncomponent dissolved therein, and it is thus considered that its crystalstructure is different from that of the inventive magnesium-aluminumoxynitride.

The XRD peaks corresponding with (111) face, (200) face and (220) faceof the MgO—AlN solid solution were shown in 2θ=36.9 to 39°, 42.9 to44.8° and 62.3 to 65.2°, respectively, which are between the peaks ofcubic phase of magnesium oxide and cubic phase of aluminum nitride. FIG.2 shows EPMA element mapping images obtained in the Experiment 1. Asshown in FIG. 2, it was proved that the material of the Experiment 1 iscomposed of the two phases of the magnesium-aluminum oxynitride (“x”part) shown in FIG. 1 and the MgO—AlN solid solution (“y” part) and thatthe former forms the main phase. Here, the main phase means a componentoccupying 50 percent or more in volume ratio, and sub-phase means aphase other than the main phase and whose XRD phase is identified. Aratio of area at an observed cross section is considered to reflect thevolume ratio, so that the main phase is defined as an area having a arearatio of 50 percent or more in an EPMA element mapping image and the subphase is defined as an area other than the main phase. As shown in FIG.2, the ratio of area of the magnesium-aluminum oxynitride was about 68percent and the magnesium-aluminum oxynitride was proved to be the mainphase. Besides, “x” part is identified as the magnesium-aluminumoxynitride, because it was composed of four components of Mg, Al, O andN, and the contents of Mg and N were higher than, Al content was closeto and O content was lower than those in spinel material (“z” part)obtained in the Experiment 4. That is, the magnesium-aluminum oxynitrideis characteristic in containing more Mg than spinel. Similar analysiswas performed for the other Experiments and, for example, it was provedthat the ratio of area of the magnesium-aluminum oxynitride was about 87percent to constitute the main phase in the Experiment 10. Further,although the judgment of the main and sub phases was performed by theEPMA element mapping according to the present example, another methodmay be applied as far as it is possible to distinguish the volume ratioof each phase.

Besides, an EPMA element mapping image is divided into colors of red,orange, yellow, yellowish green, green, blue and indigo blue dependingon the contents, so that red, indigo blue and black correspond to thehighest content, the lowest content and zero, respectively. However, asFIG. 2 is shown in monochrome, the following description is given fororiginal colors in FIG. 2 below. According to the Experiment 1, “x” and“y” parts were colored in yellowish green and red for Mg, respectively,“x” and “y” parts were colored in orange and blue for Al, respectively,and “x” and “y” parts were colored in orange and blue for N,respectively, and “x” and “y” parts were colored in aqua blue and orangefor O, respectively According to the Experiment 4, the whole area (“z”part) was colored in green for Mg, the whole area was colored in orangefor Al, the whole area was colored in black for N, and the whole areawas colored in red for O.

Further, according to the Experiment 4, as aluminum nitride was notused, the above described magnesium-aluminum oxynitride was notgenerated, so that the ceramic material contained, as the main phase,spinel (MgAl₂O₄). According to the Experiment 5, as the sinteringtemperature was low, the above described magnesium-aluminum oxynitridewas not generated, so that the ceramic material contained magnesiumoxide as the main phase and spinel and aluminum nitride as the subphases. FIGS. 3 and 4 show XRD analytical charts of the Experiments 7and 10, respectively. As can be seen from FIGS. 3 and 4, it was mainlydetected the magnesium-aluminum oxynitride (□ in the figures) havingpeaks in a range of 2θ=47 to 49° (or 47 to 50°) in the Experiments 7 and10, and spinel (Δ in the figure) and MgO—AlN solid solution (◯ in thefigure) were found as the sub phases in the Experiments 7 and 10,respectively. Besides, the XRD analytical charts were omitted as to theExperiments 6, 8, 9, 11 and 12 and the main and sub phases are shown intable 1.

Then, the etching rates of the ceramic materials of the Experiments 1 to3 and 6 to 8 were as low as 80 percent or lower, and the etching ratesin the Experiments 9 to 12 were as low as 90 percent or lower, of thatin the Experiment 4. It was thus proved that the corrosion resistancewas very high. As that of the Experiment 5 includes much amounts ofspinel and aluminum nitride with lower corrosion resistance, the etchingrate was proved to be higher. Besides, the etching rate of alumina shownin the Experiment 18 was higher than that of the ceramic material(spinel) of the Experiment 4. The ceramic materials of the Experiments 1to 3 and 6 to 8 have sufficiently high bending strengths and volumeresistivities.

It was further measured an etching rate at high temperature. Here, forthe ceramic materials of the Experiments 2 and 10, the surface of eachof the materials was polished to a mirror face and subjected tocorrosion resistance test at high temperature under the followingconditions using an ICP plasma corrosion resistance test system. Then, astep between the masked face and exposed face measured by a step gaugeis divided by a test time period to calculate the etching rate of eachmaterial. As a result, the etching rate of each material was ⅓ or lowerof that of alumina, ⅕ or lower of that of aluminum nitride, andcomparable with that of spinel, and the corrosion resistance againstplasma at high temperature was also good.

ICP: 800 W, Bias: none, Introduced gas: NF₃/Ar=300/300 sccm, 0.1 Torr,Exposed time: 5 h, Temperature of sample: 650° C.

According to the ceramic materials of the Experiments 12 to 16, theetching rate (212 to 270 nm/h) was very close to that of spinel of theExperiment 4, and the linear thermal expansion coefficient (5.8 to 6.9ppm/K) was lower than that of spinel. That is, the ceramic materials ofthe Experiments 12 to 16 were preyed to have corrosion resistancecomparable with that of spinel while providing a lower linear thermalexpansion coefficient, so that they are useful for materials of anelectrostatic chuck and heater, especially heater. Besides, although rawmaterial composition of the Experiment 17 was made identical with thatof the Experiment 6, the sintering temperature was made lower.Consequently, its main phase was not the magnesium-aluminum oxynitridebut spinel, so that its corrosion resistance was lowered and linearthermal expansion coefficient was higher compared with those of theExperiment 6. Further, the ceramic materials of the Experiments 12 to 16have sufficiently high bending strength and volume resistivity.

Further, the volume resistivities at 600° C. in the Experiments 7 and 19were 5×10⁸ Ω·cm and 2×10¹² Ω·cm, respectively. It was proved that theceramic material having, as the main phase, the magnesium-aluminumoxynitride phase having an XRD peak at least in a range of 2θ=47 to 49°(or 47 to 50°) has an electrical resistance lower than that of MgO.

As described above, it is predicted that the ceramic materials producedin the Experiments 1 to 3 and 6 to 16 also have electrical resistanceslower than that of magnesium oxide.

TABLE 1 First Second Third RelationShip Component Component componentMg/Al Sintering Bulk Open With (MgO) (Al2O3) (AlN) molar TemperatureDensity porosity invention (mass %) (mass %) (mass %) ratio (° C.)(g/cm3) (%) Exp. 1 Inventive 51.6 21.9 26.5 1.2 1850 3.40 0.04 Exp. 2Example 51.6 21.9 26.5 1.2 1800 3.37 0.03 Exp. 3 51.6 21.9 26.5 1.2 17503.38 0.03 Exp. 4 Comparative 28.2 71.8 — 0.5 1850 3.57 0.01 Exp. 5Example 51.6 21.9 26.5 1.2 1650 3.47 0.01 Exp. 6 Inventive 33.3 30.236.4 0.7 1775 3.28 0.02 Exp. 7 Example 27.6 32.8 39.6 0.4 1800 3.30 0.02Exp. 8 33.9 22.3 43.8 0.6 1800 3.28 0.01 Exp. 9 28.1 24.3 47.7 0.4 18503.25 0.02 Exp. 10 28.1 24.3 47.7 0.4 1800 3.26 0.02 Exp. 11 28.1 24.347.7 0.4 1750 3.26 0.03 Exp. 12 18.6 27.5 54.0 0.3 1800 3.33 0.02 Exp.13 9.6 11.0 79.4 0.1 1800 3.27 0.01 Exp. 14 9.6 11.0 79.4 0.1 1850 3.270.08 Exp. 15 24.2 25.5 50.2 0.4 1800 3.27 0.12 Exp. 16 9.4 19.4 71.2 0.11900 3.27 0.02 Exp. 17 Comparative 33.3 30.2 36.4 0.7 1700 3.28 0.03Exp. 18 Example 0 100 0 — 1700 3.94 0.01 Exp. 19 100 0 0 — 1500 3.570.30 Linear thermal NF₃ expansion Volume Volume Etching coefficientResistivity Resistivity Crystal phase Rate @40~1000° C. Strength @25° C.@600° C. Main phase Sub phase (nm/h) (ppm/K) (MPa) (Ω · cm) (Ω · cm)Exp. 1 Mg—Al—O—N* MgO—AlNss** 176 9.5 240 >1E16 — Exp. 2 Mg—Al—O—N*MgO—AlNss** 177 9.3 291 >1E16 — Exp. 3 Mg—Al—O—N* MgO—AlNss** 179 9.6320 >1E16 — Exp. 4 MgAl₂O₄ None 244 8.6 168 >1E16 — Exp. 5 MgO MgAl₂O₄,AlN 224 >10 350 >1E16 — Exp. 6 Mg—Al—O—N* MgO—AlNss** 181 7.7 236 >1E16— MgAl₂O₄ Exp. 7 Mg—Al—O—N* MgAl₂O₄ 191 7.3 242 >1E16 5E8  Exp. 8Mg—Al—O—N* MgO—AlNss** 195 7.6 272 >1E16 — Exp. 9 Mg—Al—O—N* MgO—AlNss**210 7.1 233 >1E16 — Exp. 10 Mg—Al—O—N* MgO—AlNss** 209 7.1 257 >1E16 —Exp. 11 Mg—Al—O—N* MgO—AlNss** 211 7.1 265 >1E16 — Exp. 12 Mg—Al—O—N*AlN, MgAl₂O₄ 219 6.9 387 >1E16 — Exp. 13 Mg—Al—O—N* AlN, MgAl₂O₄ 270 5.8304 >1E16 — Exp. 14 Mg—Al—O—N* AlN MgAl₂O₄ 255 6.0 304 >1E16 — Exp. 15Mg—Al—O—N* MgAl₂O₄ 212 6.9 283 >1E16 — Exp. 16 Mg—Al—O—N* AlN, MgAl₂O₄230 6.2 320 >1E16 — Exp. 17 MgAl₂O₄ AlN, MgO 256 8.1 400 — — Exp. 18Al₂O₃ None 623 8.0 290 — — Exp. 19 MgO — — — 240 >1E16 2E12 *Mg—Al—O—N:Magnesium-aluminum oxynitride (XRD): peaks in 2θ = 47-49°) **MgO—AlNss:Mg0—AlN solid solution ┌—┘: not measured

2. Laminated Sintering

Next, it will fee described a laminated body provided fey laminatedsintering of first and second structural bodies utilizing the ceramicmaterial described above (Experiments 20 to 26). Besides, theExperiments 20 to 24 correspond to the inventive examples and theExperiments 25 and 26 correspond to comparative examples.

Experiments 20 and 21

The ceramic materials of the Experiments 4 and 6 to 12 have averagelinear thermal expansion coefficients of 7 to 9 ppm/K in 40 to 1000° C.According to the Experiments 20 and 21, as shown table 2, the firststructural body was made of the ceramic material of the Experiment 10,and the second structural body was made of aluminum nitride. The firstand second structural bodies were laminated and molded to a provide asample having a diameter of 50 mm, which was subjected to laminatedsintering. As the aluminum nitride, it was used aluminum nitride towhich 5 mass percent of yttrium oxide was added as a sintering aid inouter addition (that is, 5 mass parts of Y₂O₃ was added to 100 massparts of AlN, referred to as AlN [1]), or aluminum nitride to which 50mass percent of yttrium oxide was added (That is, 50 mass parts of Y₂O₃was added to 100 mass parts of AlN, referred o as AlN [2]). As rawmaterials of aluminum nitride and yttrium oxide, it was used commercialproducts having a purity of 99.9 mass percent or higher and an averageparticle size of 1 μm or smaller. Here, as AlN material inevitablycontains about 1 mass percent of oxygen, the purity was calculated afteroxygen is removed from impurity elements. Further, since the averagelinear thermal expansion coefficient in 40 to 1000° C. was 5.7 ppm/K inAlN [1] and 6.2 ppm/K in AlN[2], it is provided a difference of thermalexpansion between the first and second structural bodies. Therefore,between the first and second structural bodies, it was provided anintermediate layer in which the raw materials of AlN[1] or AlN[2] andraw materials of the Experiment 10 were mixed. The difference of thermalexpansion can be relaxed by the intermediate layer. In the Experiment 20using AlN[1], the intermediate layer was composed of three layers havingmass ratios of 25:75, 50:50 and 75:25, respectively, and in theExperiment 21 using AlN[2], the intermediate layer was composed of twolayers having mass ratios or 40:60 and 60:40, respectively. It will bedescribed steps of formulation, molding and sintering below in detail.

(Formulation)

As the raw material of the first structural body, it was used formulatedpowder produced according to the similar procedure as the Experiment 10described above. The raw material of the second structural body wasproduced as described below with aluminum nitride as the main phase. InAlN [1] of the second structural body, first, aluminum nitride powderand yttrium oxide powder were weighed in a ratio of 100 mass percent and5.0 mass percent, and then wet-mixed using isopropyl alcohol as asolvent, a nylon pot and nylon agitating media for 4 hours. After themixing, slurry was collected and dried in nitrogen flow at 110° C.Thereafter, it was passed through a sieve of 30 mesh to produceformulated powder. Further, the thus obtained formulated powder wasthermally treated at 450° C. for 5 hours or longer in air atmosphere tofire and remove carbon contents included during the wet mixing. Theintermediate layer of the laminated body using AlN[1] was formulated asfollows. First, the formulated powders of the Experiment 10 and aluminumnitride described above were weighed in mass ratios of 75:25(intermediate layer 1), 50:50 (intermediate layer 2), and 25:75(intermediate layer 3), and then wet-mixed using isopropyl alcohol as asolvent, a nylon pot and nylon agitating media for 4 hours. After themixing, the slurry was collected and then dried in nitrogen flow at 110°C. Thereafter, it was passed through a sieve of 30 mesh to provideformulated powder. AlN[2] of the second structural body was producedaccording to the same procedure as AlN[1], except that the aluminumnitride powder and yttrium powder were mixed in a ratio of 100 masspercent and 50 mass percent, respectively. Further, the intermediatelayer of the laminated body using AlN[2] was formulated according to thesame procedure as AlN[1], except that the formulated powder of theExperiment 10 and that of the aluminum nitride described above weremixed in mass ratios of 60:40 (intermediate layer 1) and 40:60(intermediate layer 2), respectively.

(Molding)

First, the aluminum nitride formulated powder as the raw material of thesecond structural body was filled in a metal mold having a diameter of50 mm, and molded by uniaxial pressure molding at a pressure of 200kgf/cm². The aluminum nitride molded body was not drawn out of the mold,and formulated powders of the intermediate layers were filled thereon inthe descending order of aluminum nitride contents, while a pressure of200 kgf/cm² was applied after each of the filling procedure by uniaxialpressure molding. Lastly, the formulated powder of the Experiment 10 asthe raw material of the first structural body was filled and thenpressure molded at a pressure of 200 kgf/cm². As to the laminated bodyusing AlN[1], it was prepared a disk-shaped molded body having a totalthickness of 23 mm and including an aluminum nitride layer of 10 mm asthe second structural body, three intermediate layers each having athickness of 1 mm and the layer of the Experiment 10 as the firststructural body of 10 mm. Further, as to the laminated body usingAlN[2], it was prepared a disk-shaped molded body having a totalthickness of 22 mm and including an aluminum nitride layer of 10 mm asthe second structural body, two intermediate layers each having athickness of 1 mm and the layer of the Experiment 10 as the firststructural body. These laminated and disk-shaped bodies were containedin a graphite mold for sintering.

(Sintering)

The disk-shaped molded body contained in the graphite mold for sinteringwas subjected to hot press sintering to obtain a ceramic material byintegrated sintering. The hot press sintering was performed at apressure of 200 kgf/cm², a sintering temperature of 1800° C., and in Aratmosphere until the completion of the sintering. The holding timeperiod at the sintering temperature was made 4 hours. Besides, as to theExperiments 20 and 21, the sintering was also performed at a sinteringtemperature of 1750° C. (Experiments 20-1 and 21-1).

According to the sintered body obtained in the production methoddescribed above, in both of the laminated bodies using AlN[1](Experiments 20, 20-1) and using AlN[2] (experiments 21 and 21-1), theupper part of the sintered body was composed of the magnesium-aluminumoxynitride with high corrosion resistance, the lower part was composedof a sintered body mainly composed of aluminum nitride with high thermalconductivity and an intermediate layer was provided between them. In theintermediate layer, the Al content was inclined so that the Al contentis made higher from the first structural body toward the secondstructural body. Cracks, fractures or the like were not observed atinterfaces of the layers of the sintered bodies. It is considered thatthermal stress during the sintering could be avoided fey providing theintermediate layer between the first and second structural bodies.Further, by controlling the thermal expansion coefficient of aluminumnitride as the base material, it is possible to reduce thermal stressgenerated between the base material and the magnesium aluminumoxynitride and thereby to reduce the thickness of the intermediatelayer.

Experiments 22 to 24

According to the Experiment 22, as shown in table 2, a laminated bodywas obtained according to the same procedure as the Experiment 20,except that the first structural body was made of the ceramic materialof the Experiment 6, the second structural body was made of aluminumnitride and the laminated sintering was performed without theintermediate layer in N₂ atmosphere. According to the Experiment 23, asshown in table 2, a laminated body was obtained according to the sameprocedure as the Experiment 20, except that the first structural bodywas made of the ceramic material of the Experiment 6, the secondstructural body was made of yttrium oxide and the laminated sinteringwas performed without the intermediate layer in N₂ atmosphere. Accordingto the Experiment 24, as shown in table 2, a laminated body was obtainedaccording to the same procedure as the Experiment 20, except that thefirst structural body was made of the ceramic material of the Experiment13, the second structural body was made of aluminum nitride AlN[1] andthe laminated sintering was performed without the intermediate layer inN₂ atmosphere. In all of the Experiments 22 to 24, cracks and fractureswere not found at the interfaces between the layers. Further, accordingto each of the Experiments 22 to 24, the difference of the linearthermal expansion coefficients of the first and second structural bodieswas as low as 0.3 ppm/K or lower, so that it was possible to prevent thegeneration of cracks and fractures without providing the intermediatelayer. Besides, according to the Experiments 22 to 24, it may beprovided the intermediate layer as the Experiments 20, 20-1, 21 and21-1.

Experiments 25, 26

According to the Experiment 25, as shown in table 2, a laminated bodywas obtained according to the same procedure as the Experiment 20,except that the first structural body was composed of alumina, thesecond structural body was composed of aluminum nitride (AlN[1]), andthe laminated sintering was performed in N₂ atmosphere. According to theExperiment 26, as shown in table 2, a laminated body was obtainedaccording to the same procedure as the Experiment 20, except that thefirst structural body was composed of spinel, the second structural bodywas composed of aluminum nitride (AlN[1]), and the laminated sinteringwas performed in N₂ atmosphere. According to each of the Experiments 25and 26, cracks were generated at the interface between the layers. Thisis because the difference between the thermal expansion coefficients ofthe first and second structural bodies is too large so that it could notprevent the crack formation due to the difference of thermal expansionin spite of providing the intermediate layer.

TABLE 2 Second structural First body structural body Linear Linearthermal thermal expansion expansion coefficient Intermediate layerRelationship coefficient @40~1000° C. Presence Presence or with@40~1000° C. (ppm/ Or Sintering tem. absence of invention Material(ppm/K) Material K) Absence Structure ° C. cracks Exp. Inventive Exp.7.1 AlN 5.7 Present Three layers(first and 1800 Present 20 10 (AlN[1])second structural bodies in layers(mass ratio) = 75/25, 50/50, 25/75)Exp. Exp. 7.1 AlN 5.7 Present Three layers(first and 1750 Absent 20-1 10(AlN[1]) second structural bodies in layers(mass ratio) = 75/25, 50/50,25/75) Exp. Exp. 7.1 AlN 6.2 Present Two layers(first and 1800 Absent 2110 (AlN[2]) second structural bodies in layers(mass ratio) = 60/40,40/60) Exp. Exp. 7.1 AlN 6.2 Present Three layers(first and 1750 Absent21-1 10 (AlN[2]) second structural bodies in layers(mass ratio) = 75/25,50/50, 25/75) Exp. Exp. 6 7.7 Al₂O₃ 8.0 Absent — 1800 Absent 22 Exp.Exp. 6 7.7 Y₂O₃ 7.9 Absent — 1800 Absent 23 Exp. Exp. 5.8 AlN 5.7 Absent— 1800 Absent 24 13 (AlN[1]) Exp. Comparative Alumina 8.0 AlN 5.7Present Three layers(first and 1800 Present 25 (AlN[1]) secondstructural bodies in layers(mass ratio) = 75/25, 50/50, 25/75) Exp.Spinel 8.6 AlN 5.7 Present Three layers(first and 1800 Present 26(AlN[1]) second structural bodies in layers(mass ratio) = 75/25, 50/50,25/75)(Production and Evaluation of Heating Apparatus)

It will be described a method of producing a ceramic heater according toan embodiment of the present invention, referring to FIGS. 7, 8 and 12(Experiment Nos. 3 to 6).

-   (a) First, it was prepared materials of a susceptor (plate) (S101).    As to material of the surface corrosion resistant layer 14,    specifically, raw materials of MgO, Al₂O₃ and AlN were weighed, and    wet-mixed using isopropyl alcohol as a solvent, a nylon pot, and    alumina agitating media with a diameter of 5 mm for 4 hours. The    mixing is performed using, for example, a large scale ball mill with    its container itself rotated, which is called trommel. After the    mixing, the slurry was collected and dried in nitrogen flow at    110° C. It was then passed through a sieve of 30 mesh to produce    formulated powder. Besides, a molar ratio of Mg/Al in the formulated    powder was 1.2.

On the other hand, as to material of the plate shaped main body 13,aluminum nitride ceramic powder was mixed with a binder for molding. Thetime period of mixing by trammel was about 30 minutes, for example.Thereafter, granulation was performed by means of a granulating systemsuch as a spray drier (SD) to obtain granulated powder.

-   (b) Then, the formulated powder for the surface corrosion resistant    layer was molded by a mechanical press under uniaxial pressure, and    the granulated powder for the plate shaped main body was then added    thereto and molded by the same mechanical press under uniaxial    pressure to produce a preliminary molded body (S102). Then, a heat    generator 4 and electrical supply terminal part 6 were embedded    inside of the preliminary molded body, which was then molded by the    mechanical press again.-   (c) The laminated molded body produced as described above was    contained in a sintering furnace such as of hot press molding and    then sintered (S103). According to hot press molding, raw material    powder or molded body is filled or inserted in a carbon jig and then    sintered at uniaxial pressure of 30 to 50 MPa. This is suitable for    sintering of ceramic materials which are difficult to density by    conventional sintering at ambient pressure. The sintering conditions    are under sintering temperature of 1600 to 2000° C., a pressure of    100 to 300 kgf/cm² and sintering time period of 2 to 5 hours.-   (d) On the other hand, the supporting part (shaft part) 3 is    produced separately from the plate. First, materials of the shaft    are prepared (S104). Specifically, formulated powder is prepared    according to the same procedure as that of the plate shaped main    body (S101). The thus prepared formulated powder was contained in a    sintering furnace such as a cold isostatic press (CIP) and sintered    to produce a molded body (S105). CIP is a method of subjecting an    uniaxial molded body obtained by metal mold method to isostatic    press molding so as to improve the density of and to prevent the    ununiformity of the molded body. It is possible to directly fill the    raw materials in a rubber mold without performing the molding using    a metal mold and to perform CIP processing to obtain a molded body.    The thus obtained molded body of shaft is sintered in an ambient    pressure sintering furnace or the like (S106). The sintering    conditions include a sintering temperature of 1600 to 2000° C., a    pressure of 1 to 30 kg/cm² and a sintering time period of 1 to 5    hours. Then, the shaft is processed in its outer periphery or by    lapping (S107).-   (e) The susceptor and shaft obtained according to the procedure as    described above are bonded with each other in a sintering furnace by    direct bonding process (S108). The sintering conditions include a    sintering temperature of 1400 to 2000° C., a pressure of 100 to 300    kg/cm² and a sintering time period of 2 to 5 hours. A ceramic heater    after the bonding is subjected to processing of its side face and    connection of terminals in a bonding furnace. Thereafter, washing    treatment and evaluation of temperature uniformity are performed.

Besides, materials forming the surface corrosion resistant layers in theExperiments 3, 4, 5 and 6 in table 3 are that of the Experiment No. 10in the above Example (table 1).

(Heating Apparatus of Comparative Example 1)

As comparative example 1 (Experiment No. 1), the susceptor 2 andsupporting part 3 were formed from aluminum nitride powder (purity of99.5 percent) with 5 weight percent of yttrium oxide added and bondedwith each other to produce a heating apparatus.

(Heating Apparatus of Comparative Example 2)

As comparative example 2 (Experiment No. 2), the susceptor was formed ofthe material forming the surface corrosion resistant layer in theExperiment Nos. 3, 4, 5 and 8 in table 3. The material is that used inthe Example 12 in the example section (table 1). The supporting part 3was made from aluminum nitride powder (purity of 99.5 percent)containing 5 weight percent of yttria.

(Test Condition)

Corrosion resistance test: ICP: 800 W, Bias: 450 W, Supplied gas:NF₃/O₂/Ar=75/35/100 sccm, 0.05 Torr, Exposed time period: 100 hours,Temperature of sample 600° C.

Evaluated properties: Temperature uniformity on a wafer, amount ofparticles and surface roughness before and after the corrosionresistance test described above.

Measurement of Temperature Uniformity

The ceramic heaters of the examples were set in a vacuum chamber, and ablack body wafer for temperature measurement was set on the ceramicheater, which was heated at 550° C. Temperature distribution on theblack body wafer at the temperature was measured from the outside of thechamber by infrared ray radiation thermometer (IR camera). Based on thethus obtained temperature distribution, a difference “ΔT” between themaximum and minimum temperatures was calculated. Besides, the heating ofthe heater at the temperature was controlled by a thermocouple not shownfitted to a back face of the ceramic susceptor.

Amount of Particles:

The ceramic heaters of the examples were set in a vacuum chamber and anSi wafer was set on the ceramic heater, which was heated at 550° C. Itwas measured the amount of particles on a surface of the Si wafer on theside of the mounting face of the ceramic heater after the heating by aparticle counter. Besides, the heating of the heater at the temperaturewas controlled by a thermocouple not shown fitted to a back face of theceramic plate.

Surface Roughness:

The roughness of the product surface was measured by Tailor-Hobsonroughness measuring instrument. The measurement was performed at twooptional positions in inside and outside parts of the plane.

TABLE 3 Temperature uniformity on Surface roughness wafer (° C.)Particle amount Ra (μm) Before (counts) Before Evaluation CorrosionAfter After Before After After Corrosion After After temp. Resistance50RF 100RF Corrosion 50RF 100RF Resistance 50RF 100RF Ex. No. MaterialEmbodiment (° C.) test Hours Hours Resistance Hours Hours test HoursHours 1 AlN Com. Ex. 1 550 2.5 4.8 7.8 2,000 5,500 8,200 0.7 1.0 1.2 2Mg—Al—O—N Com. Ex. 2 550 4.0 3.8 4.1 1,500 1,600 1,600 0.7 0.7 0.7 3Hybrid Inv. Ex. 1 550 2.5 2.5 2.4 1,600 1,600 1,500 0.7 0.7 0.7 4 HybridInv. Ex. 2 550 2.4 2.5 2.5 1,400 1,300 1,400 0.7 0.7 0.7 5 Hybrid Inv.Ex. 3 550 2.6 2.6 2.6 1,200 1,200 1,300 0.7 0.7 0.7 6 Hybrid Inv. Ex. 4550 1.9 2.0 1.9 1,600 1,500 1,500 0.7 0.7 0.7

According to the Experiment No. 1, although the temperature uniformityon wafer after the corrosion resistant test was good, particles wereincreased and the surface roughness was deteriorated to result indeterioration of temperature uniformity on wafer after the corrosionresistance test. According to the Experiment No. 2, it was extremelysuperior in that the temperature uniformity on wafer was notdeteriorated even after the corrosion resistance test. According toExperiment Nos. 8 to 6, the temperature uniformity on wafer after thecorrosion resistance test was not deteriorated, as well as the initialtemperature uniformity on wafer before the corrosion resistance test wasproved to be superior than that in the Experiment No. 2.

These actions and effects are epoch-making in the field of semiconductortreating system, and it can be understood that various applications areexpected in the industries.

Although specific embodiments of the present invention have beendescribed above, the invention is not to be limited to these specificembodiments and can be performed with various changes and modifications,without departing from claims.

The invention claimed is:
 1. A heating apparatus comprising a susceptor,said susceptor comprising a heating face of heating a semiconductor:wherein said susceptor comprises a plate shaped main body and a surfacecorrosion resistant layer comprising an upper face providing saidheating face; wherein said surface corrosion resistant layer comprises aceramic material comprising magnesium, aluminum, oxygen and nitrogen asmain components; wherein said ceramic material comprises a main phasecomprising magnesium-aluminum oxynitride phase exhibiting an XRD peak atleast in 2θ=47 to 50° taken by using CuKα ray; and wherein said ceramicmaterial comprises a sub phase comprising a crystal phase of MgO—AlNsolid solution wherein aluminum nitride is dissolved into magnesiumoxide.
 2. The heating apparatus of claim 1, said susceptor furthercomprising a back face covering layer covering a back face of said plateshaped main body, said back face covering layer comprising a ceramicmaterial comprising magnesium, aluminum, oxygen and nitrogen as maincomponents, wherein said ceramic material comprises a main phasecomprising magnesium-aluminum oxynitride phase exhibiting an XRD peak atleast in 2θ=47 to 50° taken by using CuKα ray.
 3. The heating apparatusof claim 1, said susceptor further comprising a side face corrosionresistant layer covering a side face of said plate shaped main body,said side face corrosion resistant layer comprising a ceramic materialcomprising magnesium, aluminum, oxygen and nitrogen as main components,wherein said ceramic material comprises a main phase comprisingmagnesium-aluminum oxynitride phase exhibiting an XRD peak at least in2θ=47 to 50° taken by using CuKα ray.
 4. The heating apparatus of claim1, further comprising an intermediate layer provided between said plateshaped main body and at least one of said surface corrosion resistantlayer, said back face covering layer and said side face corrosionresistant layer.
 5. The heating apparatus of claim 1, further comprisinga supporting part bonded to a back face of said susceptor.
 6. Theheating apparatus of claim 5, said supporting part comprises saidceramic material.
 7. The heating apparatus of claim 5, furthercomprising: a heat generator embedded in said susceptor; and anelectrical supplying member contained in an inner space of saidsupporting part and electrically connected to said heat generator. 8.The heating apparatus of claim 1, wherein said 2θ is 47 to 49°.
 9. Theheating apparatus of claim 1, wherein said MgO—AlN solid solution hasXRD peaks at (200) and (220) faces taken by using CuKα ray in ranges of2θ=42.9 to 44.8° and 62.3 to 65.2°, respectively, which are betweenpeaks of cubic phase of magnesium oxide and cubic phase of aluminumnitride, respectively.
 10. The heating apparatus of claim 9, whereinsaid MgO—AlN solid solution has an XRD peak at (111) face taken by usingCuKα ray in a range of 2θ=36.9 to 39°, which is between peaks of cubicphase of magnesium oxide and cubic phase of aluminum nitride.
 11. Theheating apparatus of claim 1, wherein said ceramic material does notcontain AlN crystal phase.
 12. The heating apparatus of claim 1, whereinsaid plate shaped main body comprises a ceramics comprising aluminumnitride, yttrium oxide or aluminum oxide as a main phase.